Bending method

Abstract

A bending method utilizes a die including a V-groove at an upper part thereof, and a punch including a first surface and a second surface at a workpiece pressing portion. In a state of being mounted on an upper table of a press brake, the first surface is parallel to a first groove wall surface of the die mounted on a lower table. An angle formed between the second surface and a perpendicular plane is different from an angle formed between a second groove wall surface and the perpendicular plane. A plate-shaped workpiece placed on the die is bent in a state of being sandwiched between the first groove wall surface and the first surface.

The invention claimed is: 
     
         1 . A bending method of bending a plate-shaped workpiece with use of: a die mounted on a lower table of a press brake and including a V-groove having a first groove wall surface and a second groove wall surface at an upper part thereof, and a punch mounted on an upper table of the press brake and including, at a workpiece pressing portion, a first surface, a second surface, and a distal end, the first surface of the punch being parallel to the first groove wall surface of the die the distal end of the punch being provided with a tip at a lower end of the distal end, neighboring planar portions, the planar portions being continuous with the first surface and parallel to the first groove wall surface and the second groove wall surface in a state in which the punch is advanced into the V-groove, the method comprising the steps of:
 placing the plate-shaped workpiece on the upper part of the die mounted on the lower table of the press brake; and 
 pressing the plate-shaped workpiece by the workpiece pressing portion of the punch mounted on the upper table of the press brake so as to bend the plate-shaped workpiece when sandwiched between the first groove wall surface of the V-groove and the first surface of the punch, 
 wherein an angle formed between the second surface and a perpendicular plane is different from an angle formed between the second groove wall surface and the perpendicular plane, and the plate-shaped workpiece is bent apart from the second groove wall surface and toward a side of the perpendicular plane. 
 
     
     
         2 . The bending method according to  claim 1 , wherein at the workpiece pressing portion, the distal end connecting the first surface and the second surface is symmetrically formed with respect to the perpendicular plane passing through an intersect position at which imaginary planes extending downward along the respective first groove wall surface and second groove wall surface intersect with each other in a state in which the punch is mounted on the upper table. 
     
     
         3 . The bending method according to  claim 1 , wherein at the workpiece pressing portion, the distal end connecting the first surface and the second surface is asymmetrically formed with respect to the perpendicular plane passing through an intersect position at which imaginary planes extending downward along the respective first groove wall surface and second groove wall surface intersect with each other in a state in which the punch is mounted on the upper table. 
     
     
         4 . The bending method according to  claim 1 , wherein an angle formed between the first groove wall surface and the second groove wall surface of the V-groove is an acute angle.